Hydraulic pump assembly

ABSTRACT

A hydraulic pump assembly including a fluid reservoir, a body defining a fluid inlet and a fluid outlet, the fluid inlet being in fluid communication with the fluid reservoir, and a radially opposed piston pump assembly at least partially housed within the body and including a first piston pump mechanism and a second piston pump mechanism, the first piston pump mechanism being in fluid communication with the fluid inlet and having a first pump outlet, the second piston pump mechanism being in fluid communication with the fluid inlet and having a second pump outlet, wherein the first pump outlet and the second pump outlet are both in fluid communication with the fluid outlet.

FIELD

The present patent application is directed to pump assemblies and, moreparticularly, to hydraulic pump assemblies configured to supply apressurized fluid line to various auxiliary applications.

BACKGROUND

Anti-lock braking systems typically include wheel speed sensors, anelectronic control unit and a hydraulic control unit. The electroniccontrol unit is integrated with the hydraulic control unit to form ahydraulic modulator or electro-hydraulic control unit. The hydrauliccontrol unit may include a motor for pumping hydraulic fluid throughvarious channels, accumulators for storing accumulated hydraulic fluidand valves having internal components for directing hydraulic fluid tothe brakes. The electronic control unit may include a processor forreceiving signals from the speed sensors and solenoid coilscorresponding to each valve stem for actuating the valves according tocommand signals generated by the processor. The electronic control unitmay be integrated with the hydraulic control unit such that the coilscontact the valve stems, thereby forming the electro-hydraulic controlunit.

Advances in electro-hydraulic control unit technology and, inparticular, advances in the manufacture of electro-hydraulic controlunits, including the machining of the associated hydraulic controlunits, have resulted in efficiencies and economies of scale that led tomass production of electro-hydraulic control unit. As a result,anti-lock braking systems have become standard features of modernautomobiles.

Elsewhere in the art, hydraulic pumps such as gear pumps and vane pumpsare used to supply hydraulic fluid to various auxiliary applications,such as positioning applications (e.g., hydraulic door operators,conveyor belt tensioners and medical chairs and beds), recreationalvehicle applications (e.g., leveling, slideouts and tent trailers),clamping applications (e.g., tool fixtures and jigs, hydraulic brakes,crimping tools, arbor presses and truck restraints), cyclingapplications (e.g., garbage compactors, valve operators, press controls,packing equipment and indexing tables), and lifting applications (e.g.,handicap lifts, scissor lift tables and pellet movers).

It has been discovered that electro-hydraulic control unit technologymay be used to supply a highly pressurized fluid line to variousauxiliary applications, thereby providing a low-cost alternative totraditional hydraulic pumps for auxiliary applications.

SUMMARY

In one aspect, the disclosed hydraulic pump assembly may include a fluidreservoir, a body defining a fluid inlet and a fluid outlet, the fluidinlet being in fluid communication with the fluid reservoir, and aradially opposed piston pump assembly at least partially housed withinthe body and including a first piston pump mechanism and a second pistonpump mechanism, the first piston pump mechanism being in fluidcommunication with the fluid inlet and having a first pump outlet, thesecond piston pump mechanism being in fluid communication with the fluidinlet and having a second pump outlet, wherein the first pump outlet andthe second pump outlet are both in fluid communication with the fluidoutlet.

In another aspect, the disclosed hydraulic pump assembly may include afluid reservoir, a body defining a fluid inlet and a fluid outlet, thefluid inlet being in fluid communication with the fluid reservoir, aradially opposed piston pump assembly at least partially housed withinthe body and including a first piston pump mechanism, a second pistonpump mechanism and an electric motor, the electric motor including aneccentric that engages the first and second piston pump mechanisms, thefirst piston pump mechanism being in fluid communication with the fluidinlet and having a first pump outlet, the second piston pump mechanismbeing in fluid communication with the fluid inlet and having a secondpump outlet, wherein the first pump outlet and the second pump outletare both in fluid communication with the fluid outlet, a first pumpinlet check valve positioned in a first inlet fluid path within the bodybetween the fluid reservoir and the first piston pump mechanism, asecond pump inlet check valve positioned in a second inlet fluid pathwithin the body between the fluid reservoir and the second piston pumpmechanism, a first pump outlet check valve positioned in a first outletfluid path within the body between the first piston pump mechanism andthe first pump outlet, a second pump outlet check valve positioned in asecond outlet fluid path within the body between the second piston pumpmechanism and the second pump outlet, and a pressure relief valve influid communication with the fluid outlet.

Other aspects of the disclosed hydraulic pump assembly will becomeapparent from the following description, the accompanying drawings andthe appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of one aspect of the disclosedhydraulic pump assembly connected to an auxiliary application;

FIG. 2 is a side elevational view of the hydraulic pump assembly of FIG.1;

FIG. 3 is a front elevational view, shown in section, of the hydraulicpump assembly of FIG. 2;

FIG. 4 is a schematic illustration of a second aspect of the disclosedhydraulic pump assembly;

FIG. 5 is a front elevational view, shown in section, of the hydraulicpump assembly of FIG. 4;

FIG. 6 is a schematic illustration of a third aspect of the disclosedhydraulic pump assembly; and

FIG. 7 is a front elevational view, shown in section, of the hydraulicpump assembly of FIG. 6.

DETAILED DESCRIPTION

Referring to FIG. 1, one aspect of the disclosed hydraulic pumpassembly, generally designated 6, may include a radially opposed pistonpump assembly 8, a pressure relief valve 10, and a fluid reservoir 12.The radially opposed piston pump assembly 8 may include a first pistonpump mechanism 7 and a second piston pump mechanism 9, wherein theoutputs of the first and second piston pump mechanisms 7, 9 may becombined to provide a single hydraulic fluid outlet 11. The fluid outlet11 of the radially opposed piston pump assembly 8 may be in fluidcommunication with an auxiliary application 18 by way of a pressurizedfluid line 20. The pressurized fluid line 20 may supply high pressurehydraulic fluid to the auxiliary application 18 and a return fluid line22 may return hydraulic fluid from the auxiliary application 18 to thefluid reservoir 12 at atmospheric pressure.

In particular, as shown in FIG. 2, the hydraulic pump assembly 6 mayinclude the fluid reservoir 12, a hydraulic control unit body 14, and apump motor 16. The hydraulic control unit body 14 may house the radiallyopposed piston pump assembly 8 and the pressure relief valve 10, and, inresponse to rotational power supplied by the pump motor 16, may operateto draw hydraulic fluid from the fluid reservoir 12, pressurize thehydraulic fluid, communicate the hydraulic fluid to the auxiliaryapplication 18 by way of fluid line 20, and then return the hydraulicfluid to the fluid reservoir 12 by way of fluid line 22.

The fluid reservoir 12 may be any vessel capable of storing a hydraulicfluid. For example, as shown in FIGS. 2 and 3, the fluid reservoir 12may include a bottle 24 (e.g., a plastic bottle) and a cap 26 forsecuring hydraulic fluid within the bottle 24. In one aspect, the fluidreservoir 12 may be connected to the body 14 to form an integralreservoir/body/motor assembly. In an alternative aspect, the fluidreservoir 12 may be physically separated from the body 14, but in fluidcommunication with the body 14 by way of external fluid lines (notshown).

The pump motor 16 may be any appropriate motor having a motor shaft 28(FIG. 3) with an eccentric 30 (FIG. 3) extending therefrom. In oneexample, the pump motor 16 may be a 12-volt electric motor with aneccentric 30 of about 0.85 mm to about 1.20 mm. In another example, thepump motor 16 may be a 24-volt motor. In another example, the pump motor16 may be 10-volt motor. However, those skilled in the art willappreciate that the size of the pump motor 16, the shaft 28 and theeccentric 30 will be dictated by design considerations.

As shown in FIG. 2, the pump motor 16 may be connected to the body 14such that, as shown in FIG. 3, the motor shaft 28 and associatedeccentric 30 extend into the shaft chamber 38 (discussed below) definedin the body 14 for engagement with the first and second pistons 66, 76(discussed below). Therefore, rotational power from the pump motor 16may be translated into flow and pressurization of hydraulic fluid withinthe body 14.

Referring to FIG. 3, the body 14 may be a block of rigid material, suchas aluminum, and may define a first fluid inlet bore 30, a second fluidinlet bore 32, a first piston bore 34, a second piston bore 36, a shaftchamber 38, a first fluid outlet bore 40, a second fluid outlet bore 42,a connecting bore 44, a pressure relief bore 46 and a fluid return bore48. The bores 30, 32, 34, 36, 40, 42, 44, 46, 48 and chamber 38 may bemachined into the body 14 using any available technique (e.g.,drilling). Plugs (discussed in greater detail below), such as ballplugs, may be inserted into the bores to seal the bores as appropriate.

The first fluid inlet bore 30 may be in fluid communication with thefluid reservoir 12 at a first end thereof and the first piston bore 34at a second end thereof, and may define a valve seat 50 therein. Aspring-loaded ball 52 may be received in the first fluid inlet bore 30and may be biased into engagement with the valve seat 50, therebydefining a first pump inlet check valve 54 between the first fluid inletbore 30 and the first piston bore 34. The first pump inlet check valve54 may allow hydraulic fluid to flow from the fluid reservoir 12 to thefirst piston pump mechanism 7, but not in the reverse direction.

The second fluid inlet bore 32 may be in fluid communication with thefluid reservoir 12 at a first end thereof and the second piston bore 36at a second end thereof, and may define a valve seat 56 therein. Aspring-loaded ball 58 may be received in the second fluid inlet bore 32and may be biased into engagement with the valve seat 56, therebydefining a second pump inlet check valve 60 between the second fluidinlet bore 32 and the second piston bore 36. The second pump inlet checkvalve 60 may allow hydraulic fluid to flow from the fluid reservoir 12to the second piston pump mechanism 9, but not in the reverse direction.

The first piston bore 34 may include a plug 62 sealing a first endthereof and may connect with the shaft chamber 38 at a second endthereof. The first piston bore 34 may fluidly couple the first fluidinlet bore 30 with the first fluid outlet bore 40 (i.e., the outlet ofthe first piston pump mechanism 7) and may include a first pump outletcheck valve 64 positioned between the first fluid inlet bore 30 and thefirst fluid outlet bore 40. The first pump outlet check valve 64 mayallow hydraulic fluid to flow from the first piston bore 34 to the firstfluid outlet bore 40, but not in the reverse direction.

A first piston 66 may be closely and sideably received in the firstpiston bore 34. A seal 68 may create a fluid-tight seal across the firstpiston 66 such that hydraulic fluid does not pass across the firstpiston 66 from the first piston bore 34 and into the shaft chamber 38. Abiasing element 70, such as a coil spring, may bias the first piston 66out of the first piston bore 34 and in the direction of the shaftchamber 38 for engagement with the eccentric 30 of the shaft 28 of thepump motor 16.

The second piston bore 36 may include a plug 72 sealing a first endthereof and may connect with the shaft chamber 38 at a second endthereof. The second piston bore 36 may fluidly couple the second fluidinlet bore 32 with the second fluid outlet bore 42 (i.e., the outlet ofthe second piston pump mechanism 9) and may include a second pump outletcheck valve 74 positioned between the second fluid inlet bore 32 and thesecond fluid outlet bore 42. The second pump outlet check valve 74 mayallow hydraulic fluid to flow from the second piston bore 36 to thesecond fluid outlet bore 42, but not in the reverse direction.

A second piston 76 may be closely and sideably received in the secondpiston bore 36. A seal 78 may create a fluid-tight seal across thesecond piston 76 such that hydraulic fluid does not pass across thesecond piston 76 from the second piston bore 36 and into the shaftchamber 38. A biasing element 80, such as a coil spring, may bias thesecond piston 76 out of the second piston bore 36 and in the directionof the shaft chamber 38 for engagement with the eccentric 30 of theshaft 28 of the pump motor 16 (FIG. 2).

As the pump motor 16 rotates the shaft 28 and associated eccentric 30,the eccentric 30 alternately acts on the first and second pistons 66, 76such that the pistons 66, 76 are urged into the associated first andsecond piston bores 34, 36. Then, when the eccentric 30 passes, thebiasing elements 70, 80 urge the associated pistons 66, 76 out of theassociated piston bores 66, 76.

Accordingly, due to the reciprocating action of the pistons 66, 76caused by the pump motor 16 and the biasing elements 70, 80, hydraulicfluid is drawn from the fluid reservoir 12, through the first and secondpump inlet check valves 54, 60, and into the first and second pistonbores 34, 36 when the pistons 66, 76 are urged out of the associatedpiston bores 34, 36 by the biasing elements 70, 80. Then, when thepistons 66, 76 are urged into the associated piston bores 34, 36 by theeccentric 30, the hydraulic fluid in the piston bores 34, 36 is urgedthrough the first and second pump outlet check valves 64, 74 and intothe first and second fluid outlet bores 40, 42, thereby operating as theradially opposed piston pump assembly 8.

The first fluid outlet bore 40 may include a first end 82 and a secondend 84. The first end 82 of the first fluid outlet bore 40 may beconnected to the first piston bore 34 and a first end 86 of theconnecting bore 44. The second end 84 of the first fluid outlet bore mayinclude a plug 88, such as a ball plug, received therein to form anexternal seal.

The second fluid outlet bore 42 may include a first end 90 and a secondend 92. The first end 90 of the second fluid outlet bore 42 may beconnected to the second piston bore 36 and a second end 94 of theconnecting bore 44. (A plug 96, such as a ball plug, may be used to sealthe external portion of the second end 94 of the connecting bore 44.)The second end 92 of the second fluid outlet bore 42 may be connected toan outlet port 93, which may be connected to the pressurized fluid line20 for directing hydraulic fluid to the auxiliary application 18 (FIG.2).

Thus, the connecting bore 44 may combine the first and second fluidoutlet bores 40, 42 (i.e., both outputs of the radially opposed pistonpump assembly 8) into a single fluid outlet port 93.

Still referring to FIG. 3, the pressure relief bore 46 may define avalve seat 98 therein and may include a first end 100 in fluidcommunication with the connecting bore 44 and a second end 102 havingthreads formed therein. A spring-loaded ball 104 or the like may bepositioned in the pressure relief bore 46 to engage the valve seat 98and form a pressure sensitive seal therebetween, thereby operating asthe pressure relief valve 10. A return bore 106 extending between thefluid reservoir 12 and the pressure relief bore 46 may fluidly couplethe pressure relief bore 46 with the fluid reservoir 12. The return bore106 may be connected to the pressure relief bore 46 at a point betweenthe valve seat 98 and the second end 102 of the pressure relief bore 46.

A pressure relief control screw 108 may engage the threads at the secondend 102 of the pressure relief bore 46 and a seal 110 may provide afluid tight seal between the pressure relief bore 46 and the pressurerelief control screw 108. Rotation of the pressure relief control screw108 about the threads may compress the spring-loaded ball 104, therebyurging the spring-loaded ball 104 against the valve seat 98 with greaterforce, thereby increasing the amount of fluid pressure that may beresisted by the spring-loaded ball 104 before the spring-loaded ball 104is displaced from the valve seat 98 to release hydraulic fluid to thefluid reservoir 12 through the return bore 106.

The fluid return bore 48 may include a first end 112 and a second end114. The first end 112 of the fluid return bore 48 may be in fluidcommunication with the fluid reservoir 12. The second end 114 of thefluid return bore 48 may be connected to a return port 116. The returnport 116 may be connected to the return fluid line 22 for directingreturn fluid to the fluid reservoir 12.

At this point, those skilled in the art will appreciate that the body 14of the hydraulic pump assembly 6 may be formed by machining a solidblock of material (e.g., aluminum) to form a plurality of bores havingthe desired configuration and geometry, and inserting the necessaryplugs and components (e.g., pistons, check valves and biasing elements)into the bores to form the radially opposed piston pump assembly 8 thatdelivers a single, high pressure fluid outlet and the pressure reliefvalve 10 that controls excess fluid pressure within the hydraulic pumpassembly 6.

Accordingly, those skilled in the art will appreciate that the disclosedhydraulic pump assembly 6 may provide a low-cost, high-volume radial twopiston pump and motor assembly with an integral pressure relief valve,and, optionally, an integral plastic fluid reservoir.

Referring to FIGS. 4 and 5, a second aspect of the disclosed hydraulicpump assembly, generally designated 200, may include a hydraulic controlunit body 201 (FIG. 5), a pump motor 203 (FIG. 4), a pressure reliefvalve 204, a fluid reservoir 206 and a manual control valve 208. Thehydraulic control unit body 201 and the pump motor 203 may combine toform a radially opposed piston pump assembly 202. The radially opposedpiston pump assembly 202, the pressure relief valve 204 and the fluidreservoir 206 may be configured in the manner described above inconnection with the hydraulic pump assembly 6. However, those skilled inthe art will appreciate that the radially opposed piston pump assembly202, the pressure relief valve 204 and the fluid reservoir 206 may beconfigured in various ways.

The manual control valve 208 may be a three-position, two-waybi-direction spool valve having a moveable spool 213 received in a bore209 defined in the body 201 of the assembly 200. The manual controlvalve 208 may be in communication with the combined fluid output 211 ofthe radially opposed piston pump assembly 202 by way of a first fluidchannel 210, the fluid reservoir 206 by way of a second fluid channel212, a first bi-directional input/output port 214 and a secondbi-directional input/output port 216. Those skilled in the art willappreciate that the combined fluid output 211, the first and secondfluid channels 210, 212 and the first and second input/output ports 214,216 may be formed as bores machined into the body 201 of the assembly200.

As shown in FIG. 4, the first and second input/output ports 214, 216 maybe in fluid communication with an auxiliary application 218 by way offirst and second fluid lines 220, 222. The auxiliary application 218 isshown in FIG. 4 as a hydraulic cylinder; however, those skilled in theart will appreciate that the auxiliary application 218 may be anyauxiliary device that can be manipulated by the application ofpressurized hydraulic fluid.

In the first (e.g., left) position (not shown), the spool 213 may beshifted in the direction of arrow C (FIG. 5) such that the manualcontrol valve 208 may connect the first input/output port 214 with thefirst fluid channel 210 (i.e., the pressurized fluid) by way of a firstvalve bore 230 and the second input/output port 216 with the secondfluid channel 212 (i.e., the reservoir) by way of a second valve bore232. In the first position, the first input/output port 214 may bepressurized while the second input/output port 216 may be depressurized,thereby pressurizing the piston chamber 224 of the auxiliary application218 and depressurizing the rod chamber 226 of the auxiliary application218.

In the second (e.g., middle) position (shown in FIG. 4), the spool 213may be centered in the bore 209 such that the first fluid channel 210(i.e., the pressurized fluid) is in fluid communication with a thirdvalve bore 234, which is not in fluid communication with either thefirst input/output port 214 or the second input/output port 216, and thesecond fluid channel 212 (i.e., the reservoir) is in fluid communicationwith a fourth valve bore 236, which is not in fluid communication witheither the first input/output port 214 or the second input/output port216. Therefore, in the second position, the manual control valve 208locks hydraulic fluid in the first and second input/output ports 214,216, thereby locking the auxiliary application 218 in a fixed position.

In the third (e.g., right) position (not shown), the spool 213 may beshifted in the direction of arrow D (FIG. 5) such that the manualcontrol valve 208 may connect the first input/output port 214 with thesecond fluid channel 212 (i.e., the reservoir) by way of a fifth valvebore 238 and the second input/output port 216 with the first fluidchannel 210 (i.e., the pressurized fluid) by way of a sixth valve bore240. In the third position, the first input/output port 214 may bedepressurized while the second input/output port 216 may be pressurized,thereby depressurizing the piston chamber 224 of the auxiliaryapplication 218 and pressurizing the rod chamber 226 of the auxiliaryapplication 218.

Accordingly, those skilled in the art will appreciate that the disclosedhydraulic pump assembly 200 may provide a low-cost, high-volume radialtwo piston pump and motor assembly with an integral pressure reliefvalve, an integral plastic fluid reservoir, and an integralthree-position, bi-directional spool valve for manual pressure control.

Referring to FIGS. 6 and 7, a third aspect of the disclosed hydraulicpump assembly, generally designated 300, may include a hydraulic controlunit body 301, a pump motor 303, a pressure relief valve 304, a fluidreservoir 306, a first normally closed solenoid actuated poppet valve308 (actuated by electric switch 314), and a second normally closedsolenoid actuated poppet valve 310 (actuated by electric switch 316).The hydraulic control unit body 301 and the pump motor 303 may combineto form a radially opposed piston pump assembly 302 (actuated byelectric switch 312), The radially opposed piston pump assembly 302, thepressure relief valve 304 and the fluid reservoir 306 may be configuredin the manner described above in connection with the hydraulic pumpassembly 6. However, those skilled in the art will appreciate that theradially opposed piston pump assembly 302, the pressure relief valve 304and the fluid reservoir 306 may be configured in various ways.

Furthermore, the hydraulic pump assembly 300 may include a first,constant high pressure outlet port 318 and a second, variable pressureoutlet port 320. The first outlet port 318 may be in fluid communicationwith the radially opposed piston pump assembly 302 by way of a firstbore 322 and a rod chamber 324 of a hydraulic cylinder 326 by way of afirst fluid line 328 (FIG. 6). The second outlet port 320 may be influid communication with the radially opposed piston pump assembly 302by way of a second bore 330, the fluid reservoir 306 by way of a thirdbore 332, and a rod chamber 334 of the hydraulic cylinder 326 by way ofa second fluid line 336 (FIG. 6). The second bore 330 may be interruptedby the first normally closed solenoid actuated poppet valve 308 and thethird bore 332 may be interrupted by the second normally closed solenoidactuated poppet valve 310.

In a first configuration of the disclosed hydraulic pump assembly 300,the radially opposed piston pump assembly 302 may be actuated by theswitch 312, but the first and second solenoid actuated poppet valves308, 310 may not actuated, thereby locking the hydraulic cylinder 326.In a second configuration of the disclosed hydraulic pump assembly 300,the radially opposed piston pump assembly 302 may be actuated by theswitch 312, the first solenoid actuated poppet valve 308 may be actuatedby the switch 314, and the second solenoid actuated poppet valve 310 maynot be actuated, thereby pressurizing the piston chamber 334 and drivingthe piston 335 in the direction shown by arrow A. (Equal pressures inthe piston and rod chambers 334, 324, but the rod chamber 324 has lesssurface area due to the rod.) In a third configuration of the disclosedhydraulic pump assembly 300, the radially opposed piston pump assembly302 may be actuated by the switch 312, the second solenoid actuatedpoppet valve 310 may be actuated by the switch 316, and the firstsolenoid actuated poppet valve 308 may not be actuated, therebypressurizing the rod chamber 324 and driving the piston 335 in thedirection shown by arrow B. In a fourth configuration of the disclosedhydraulic pump assembly 300, the radially opposed piston pump assembly302 may be actuated by the switch 312, the first solenoid actuatedpoppet valve 308 may be actuated by the switch 314, and the secondsolenoid actuated poppet valve 310 may be actuated by the switch 316,thereby freeing the hydraulic cylinder 326 and removing the load fromthe radially opposed piston pump assembly 302.

Accordingly, those skilled in the art will appreciate that the disclosedhydraulic pump assembly 300 may provide a low-cost, high-volume radialtwo piston pump and motor assembly with an integral pressure reliefvalve, an integral plastic fluid reservoir, and integral solenoidactuated poppet valves allowing for remote operation and full pressurecontrol using electric switches.

Although various aspects of the disclosed hydraulic pump assembly havebeen shown and described, modifications may occur to those skilled inthe art upon reading the specification. The present application includessuch modifications and is limited only by the scope of the claims.

1. A hydraulic pump assembly comprising: a fluid reservoir; a bodydefining a fluid inlet and a fluid outlet, said fluid inlet being influid communication with said fluid reservoir; and a radially opposedpiston pump assembly at least partially housed within said body andincluding a first piston pump mechanism and a second piston pumpmechanism, said first piston pump mechanism being in fluid communicationwith said fluid inlet and having a first pump outlet, said second pistonpump mechanism being in fluid communication with said fluid inlet andhaving a second pump outlet, wherein said first pump outlet and saidsecond pump outlet are both in fluid communication with said fluidoutlet.
 2. The hydraulic pump assembly of claim 1 further comprising apressure relief valve in fluid communication with said fluid outlet. 3.The hydraulic pump assembly of claim 2 wherein said pressure reliefvalve includes a biasing element that urges a ball into engagement witha valve seat.
 4. The hydraulic pump assembly of claim 3 wherein saidpressure relief valve further includes a pressure relief control screw,said biasing element being positioned between said ball and saidpressure relief control screw.
 5. The hydraulic pump assembly of claim 1wherein said fluid reservoir includes a bottle and a cap, said capsealingly engaging said bottle.
 6. The hydraulic pump assembly of claim1 wherein said radially opposed piston pump assembly includes a motorconnected to said body, said motor having a shaft with an eccentric. 7.The hydraulic pump assembly of claim 6 wherein said eccentricoperatively engages said first and said second piston pump mechanisms.8. The hydraulic pump assembly of claim 6 wherein said motor is anelectric motor.
 9. The hydraulic pump assembly of claim 6 wherein saidfirst piston pump mechanism includes a first piston biased intoengagement with said eccentric and said second piston pump mechanismincludes a second piston biased into engagement with said eccentric. 10.The hydraulic pump assembly of claim 1 further comprising a first pumpinlet check valve positioned in a first fluid path within said bodybetween said fluid reservoir and said first piston pump mechanism and asecond pump inlet check valve positioned in a second fluid path withinsaid body between said fluid reservoir and said second piston pumpmechanism.
 11. The hydraulic pump assembly of claim 1 further comprisinga first pump outlet check valve positioned in a first fluid path withinsaid body between said first piston pump mechanism and said first pumpoutlet and a second pump outlet check valve positioned in a second fluidpath within said body between said second piston pump mechanism and saidsecond pump outlet.
 12. The hydraulic pump assembly of claim 1 furthercomprising a spool valve received within said body, said spool valvebeing disposed in a fluid channel between said fluid outlet and saidfirst and second pump outlets.
 13. The hydraulic pump assembly of claim12 wherein said spool valve includes a first input/output and a secondinput/output, and wherein said spool valve is configurable between afirst position, wherein said first input/output is in fluidcommunication with said fluid output, a second position, wherein saidfluid output is decoupled from said first input/output and said secondinput/output, and a third position, wherein said second input/output isin fluid communication with said fluid output.
 14. The hydraulic pumpassembly of claim 1 wherein said first pump outlet and said second pumpoutlet are combined to form a combined pump outlet, said combined pumpoutlet being in fluid communication with a constant pressure outlet portand a variable pressure outlet port, and wherein a first normally closedsolenoid actuated poppet valve is disposed in a first fluid line betweensaid variable pressure outlet port and said combined pump outlet, saidfirst normally closed solenoid actuated poppet valve being received, atleast partially, within said body.
 15. The hydraulic pump assembly ofclaim 14 further comprising a second normally closed solenoid actuatedpoppet valve disposed in a second fluid line between said variablepressure outlet port and said fluid reservoir, said second normallyclosed solenoid actuated poppet valve being received, at leastpartially, within said body.
 16. A hydraulic pump assembly comprising: afluid reservoir; a body defining a fluid inlet and a fluid outlet, saidfluid inlet being in fluid communication with said fluid reservoir; aradially opposed piston pump assembly at least partially housed withinsaid body and including a first piston pump mechanism, a second pistonpump mechanism and an electric motor, said electric motor including aneccentric that engages said first and said second piston pumpmechanisms, said first piston pump mechanism being in fluidcommunication with said fluid inlet and having a first pump outlet, saidsecond piston pump mechanism being in fluid communication with saidfluid inlet and having a second pump outlet, wherein said first pumpoutlet and said second pump outlet are both in fluid communication withsaid fluid outlet; a first pump inlet check valve positioned in a firstinlet fluid path within said body between said fluid reservoir and saidfirst piston pump mechanism; a second pump inlet check valve positionedin a second inlet fluid path within said body between said fluidreservoir and said second piston pump mechanism; a first pump outletcheck valve positioned in a first outlet fluid path within said bodybetween said first piston pump mechanism and said first pump outlet; asecond pump outlet check valve positioned in a second outlet fluid pathwithin said body between said second piston pump mechanism and saidsecond pump outlet; and a pressure relief valve in fluid communicationwith said fluid outlet.
 17. The hydraulic pump assembly of claim 16wherein said pressure relief valve includes a biasing element that urgesa ball into engagement with a valve seat, and a pressure relief controlscrew, said biasing element being positioned between said ball and saidpressure relief control screw.
 18. The hydraulic pump assembly of claim16 wherein said fluid reservoir includes a bottle and a cap sealingengaged with said bottle.
 19. The hydraulic pump assembly of claim 16further comprising a three-position, bi-directional spool valve at leastpartially received in said body, said spool valve being in fluidcommunication with said fluid outlet.
 20. The hydraulic pump assembly ofclaim 16 further comprising a normally closed solenoid actuated poppetvalve at least partially received in said body, said solenoid actuatedpoppet valve being in fluid communication with said fluid outlet.